A radio access network (RAN) is a collection of network elements that enables calls to occur between mobile subscribers. Such a network includes nodes that carry voice traffic, signaling traffic, and a combination of voice traffic and signaling traffic. FIG. 1 illustrates a prior art radio access network used to provide wireless communication service to mobile subscribers. Such RAN network architectures include a number of functional components including transceiver stations 100, radio network controllers (RNCs) 102, and a core network 104. Core network 104 includes asynchronous transfer mode (ATM) network elements, such as ATM switches, that carry voice and signaling traffic relating to communications to and from mobile subscribers. As such, these switches are required to implement a variety of different communication protocol layers, including various ATM and SS7 protocol layers. Implementing multiple different protocol layers in the core network may be undesirable because it increases the complexity of core network elements, such as ATM switches.
FIG. 2 illustrates exemplary communication protocol layers that are implemented on interconnection point lu between core network 104 and a radio network controller 102, as illustrated in FIG. 1. In the illustrated example, three different types of messages are communicated between the core network and the RNC over the connection point lu. One type of message is represented protocol stack 200. Protocol stack 200 is used to carry radio access network application part (RANAP) messages between the core network and the RNC. RANAP messages are radio network signaling messages. The next layer in protocol stack 200 is the signaling connection control part (SCCP) layer. This layer performs SS7 functions, such as global title translation. The next layer is message transfer part layer 3 broadband (MTP3B), which carries large payloads (4091 bytes versus 272 bytes for normal MTP3) of SS7 traffic. The next three layers, the service specific coordination function network to network interface (SSCF-NNI) layer, the service specific connection oriented protocol (SSCOP) layer, and the ATM adaptation layer 5 (AAL5), are related to the ATM protocol. The AAL5 layer supports connection-oriented variable bit rate data services. The SSCOP layer provides TCP-like services, such as flow control, timeouts, and retransmissions for ATM networks. The purpose of the SSCF-NNI layer is to enhance the service of SSCOP to meet the needs of the NNI level 3 protocol. In addition, the SCCF at the NNI provides communication with layer management for the proper operation of signaling links. Finally, the network layer, just above the physical layer is the ATM layer, which provides for the establishment of virtual circuits and transmission of ATM cells between endpoints.
Protocol stack 202 carries call setup messages for radio access networks. For example, Q.2630.1 messages are used for ATM bearer connection establishment and the binding of an ATM bearer connection or channel to a telephony connection. As used herein, Q.2630.1 refers to functionality described in International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Recommendation Q.2630.1, Sep. 29, 1999, the disclosure of which is incorporated herein by referenced in its entirety. The Q.2510.1 layer provides AAL type 2 signaling transport converter service for broadband MTP. As used herein, the Q.2510.1 layer refers to functions described in ITU-T Recommendation Q.2510.1, Jun. 23, 1999, the disclosure of which is incorporated in herein in its entirety. The remaining layers in protocol stack 202 are ATM layers that perform the same or similar functions to the correspondingly-named layers of protocol stack 200.
Protocol stack 204 carries user data, such as digitized voice, between the RNC and the core network. As such, protocol stack 204 includes a user part layer that contains the actual user data, an AAL2 layer, which supports connection-oriented services that do not require constant bit rates, such as variable bit rate video applications.
Providing the multiple protocol layers illustrated in FIG. 2 in core network elements, such as ATM switches, increases the complexity and cost of these elements. Accordingly, there exists a long-felt need for methods and systems for communicating between the core network and radio network controllers that reduces the complexity of core network elements.